1. Field of the Invention
The invention pertains to a process for enriching keratinocyte stem cells.
The invention also pertains to keratinocyte stem cells having a high expansion potential.
2. Description of Related Art
Hematopoietic tissue and skin have similarities at the level of their organization. These are dynamic and hierarchized biological systems, in which large quantities of mature cells are continuously produced and renewed, throughout the life of the individual. The cells of which they are composed can be diagrammatically classified in 3 compartments according to their stage of evolution. However, there are no clearly defined boundaries between these compartments, each one of them being in reality constituted by a continuum of cells with a variable degree of maturation, and therefore very heterogeneous.
A first compartment is composed of differentiated mature cells the proliferation potential of which is very limited or nil (lymphocytes, macrophages, megacaryocytes, erythrocytes; keratinocytes of the suprabasal layers of the epidermis).
A second compartment includes a population of cells which have a variable but limited proliferation potential which they gradually lose by becoming committed towards differentiation (hematopoietic progenitors and precursors; keratinocytes in transitory amplification phase).
A third compartment is constituted by rare cells situated upstream in the hierarchy of these systems. It includes the stem cells (hematopoietic stem cell; keratinocyte stem cell) in particular characterized by the fact that, although mostly remaining in a state of quiescence, these cells have a very considerable long term expansion potential, but also in particular characterized by their self-renewal ability.
The phenotype of the keratinocyte stem cells having thus far been only imperfectly characterized, these cells remain at present difficult to purify, difficult to select, and consequently at present no effective process for enrichment of keratinocyte stem cells is available.